Ocular tissues of various animals and humans were studied by transmitting and scanning electron microscopy. A great number of pathological materials obtained through surgery and autopsy at the NIH Clinical Center was the main source. Also, many unusual clinicopathological materials which were sent for consultation from various parts of the country were studied in this project. The most extensively studied projects were: development of the prenatal rat retina, development of the optic nerve toxic effect of cyanide to the optic nerve, optic neuropathy by para-chlorophenylalanine, fine structure of the lens, fine structure of the pigment epithelium, microcystic degeneration of the cornea, Peters' anomaly, structure of eye lid muscle and effect of hyperosmotic fluid in the ciliary epithelium.